Back to a Frozen Future
by geometrynerd
Summary: The "road" trip Anna's older sister surprised her with wasn't quite what she expected. Inspired heavily by the Back to the Future trilogy.
1. Prologue

**Prologue**

Hurtling through time and space was not, Anna mused, what she had imagined when she suggested that she, her older sister Elsa, and her boyfriend Kristoff go on road trip to "bond as a family and have lots of adventures and stuff!"

But now, even as she sat in the cramped front seat of her sister's car, trying hard not to wake Kristoff from the deep slumber he'd succumbed to, she knew this was even better than what she ever dreamt of doing as a family adventure.

She looked at her muttering, frustrated sister whose death grip on the steering wheel turned her knuckles bone-white.

The whole "fighting evil ex's minions" thing, though, she could have done without, even if she finally was able to put her Tae Kwon Do skills to use.


	2. Chapter 1

It was the absence of any comment, not even a teasing one directed at Anna, or a sarcastic quip about one of Kristoff's anecdotes, that signaled to the young couple that there were strange circumstances afoot regarding Anna's older sister Elsa.

This particular young woman, though often caught in a daze of intense thought (about what, Anna was unsure), was not known to pass up the opportunity to deliver a sarcastic, witty response. Even during the Incident from years past, she had never been known to spare Anna of the gentle teasing comments older sisters tend to make.

It was the sly grin on her face that betrayed the elder.

"What do you mean, _am I plotting something_?" she responded with a smirk at Anna's question. Was that, Anna noted, a glint suggesting mischief shining faintly in the eyes of her secretive sister?

"You know what I mean, Elsa. You even have that _mad scientist_ grin thing you do when you…do things." Anna flailed her arms to demonstrate, nearly knocking over the tray a passing waiter carried. He recovered at a moment's notice, but made a mental note to avoid the proximity in which the redhead sat.

"_Do things_, Anna?" said Kristoff disapprovingly, his eyebrow raised as he looked at his more-than-a-friend.

"You know what I mean," Anna breathed out, feeling increasingly more exasperated as they sat at that booth.

Kristoff, being privy to the kind of unspoken communication to which the elder sister was prone, glanced at Elsa, then sat back with a bemused smile on his face.

"_Okay_, you two. What's going on here?" Anna glared at them both in a look (she hoped) that indicated her suspicion.

"You know that road trip you won't shut up about?" Kristoff smirked.

"Wuh–what do you mean, _won't shut up about_, Kristoff?" she put her fists at her hips, mimicking the stern pose she had often seen her teachers make whenever she did something they considered improper.

"Anna," Elsa chuckled, "you've been on about since you first brought it up…six months ago."

Kristoff snickered.

"Okay, but…what about it?"

Elsa, the stinker that she was, merely smirked in response.

"Anna, I'm going by myself, and that is _final_."

"But Elsa!" responded the _other_ stubborn sister.

"And _please_ don't run after me this time. _Please_."

"But-"

"Anna, _please_. I don't want you to get hurt."

The way Elsa was acting, one would have thought she had some sort of shady dealings with certain foreign agents to obtain illegal nuclear substances.

"Fine…Wait, what? What do you mean 'get hurt'? Where are you going? Is it safe? Will _you_ be safe? You know I know Tae Kwon Do, and I took Kend too, remember? I can totally help fight off any goons you might–"

"Please, Anna. _Just stay here_. I'm just going to meet with some…er, 'friends'", Elsa narrowed her eyes, "to..negotiate over some, uh, _important_, er, deals? Deals. Yes, that's it. I'm having some meetings. You know. "

"Okay…I really hope you're not making shady deals with foreign agents to get like, plutonium or something."

Elsa's eyes widened, her mouth slightly agape.

"I-I-I have to go." Then she turned from Anna, not looking back once as she sped off in her clunky car from the '80s or whatever time period it was. Anna always thought her sister was some kind of car hipster because of it.

She briefly considered hopping on her skateboard and chasing after her stubborn, secretive, and totally a stinker sister, but knew that even she, a veritable speed demon, couldn't catch up to the speedier (for now) sister.

"We _have_ to go after her, Kristoff." Anna was walking several steps apace of Kristoff, making deliberate, forceful steps as she moved.

"Anna, we've been through this. I'm sure Elsa's alright. She's twenty-four, not four. I'm sure she can look after herself."

While he didn't quite believe everything he was saying, the desperate look on his girlfriend's face told him he ought to try to reassure her. That's what good couples do, right? Right?

Sure, it was already a day and a half past the date Elsa was supposed to have come back, but surely, she wouldn't have sent them a voicemail just that morning if she was in danger? Right?

And surely he was doing what good friends were supposed to do when they were going to surprise their friend's younger sister with a family vacation/road trip across the land, right?

"And besides, she's like, what? Three years older than you." He waved his hands around, as if to emphasize his point. "Elsa's supposed to be the overprotective one, feisty pants, not you."

He had caught up to her at last, then gave her a faint smile.

Anna sighed as he stood beside her. He wrapped his arms around her, her head leaning instinctively towards his shoulder. He leaned his head to meet hers.

"I'm just a little worried, Kristoff….remember the _last time_ Elsa disappeared by herself?" Anna frowned.

"Yeah but…but," Kristoff rubbed his neck, "she gave warning this time?" His voice crackled, then his lips formed into a nervous grin as Anna separated herself and stood away from him, glaring.

Suddenly, something skidded past them, nearly colliding with a neighbor's car.

The grey DeLorean suddenly lurched backwards near the couple whose afternoon walk had suddenly been interrupted.

"GET IN!" Elsa shouted frantically. "BOTH OF YOU! NOW!"


	3. Chapter 2

The doors hissed when they swung up, revealing the elder Andersen sister struggling to slow the pace of her breathing, her hands clasped tightly around the handles of the steering wheel.

The first thing Anna noticed when she peered into the car wasn't that Elsa was wearing a completely opaque pair of glasses that looked like they were made from one sheet of metal (how could she even see in those things?), or that she was wearing two large yellow rubber gloves as she grasped at the handles of the steering wheel. Because that wasn't all totally weird to begin with.

Or even that she was wearing a white lab coat over one of her many plaid shirts (not that such an outfit was out of the ordinary for her older sister, who seemed to wear the same combination of collared plaid shirts and slacks every day. _It's more efficient this way_, she remembered Elsa saying when she had asked her about her repetitive choice of clothing).

It was the machinery that had been added in the back of the DeLorean, a nest of wires and tubes that glowed a phosphorescent blue even in the light of day, that made Anna freeze in wonder and confusion. What the _hell_ did her sister do to her car?

"Elsa! Where—what—" Anna sputtered out loudly. "Where have you—w-w-hat did you-How do you—how do you even _see_ in those things?"

Elsa released her grip on the wheel then placed her shaking hands, palms down, at her thighs. She muttered something to herself, her chest rising as she inhaled. After a few moments, her hands stilled.

"I'll explain in a bit," she said with an even voice, "just get in. Please."

Spurred by her older sister's use of what she called the "queenly, regal, commanding" voice, Anna slid into the front seat; Kristoff followed after, barely able to squeeze into the front seat alongside the young woman.

"You know," Kristoff grunted, "we could have taken my van."

"Oh Kristoff. Your rusty, aging, van," Elsa lifted the glinting, opaque shades up to her forehead, turning behind her, "wouldn't have and will not survive the two point nine-nine-seven times ten to the eight meters per second speed," she said flatly as she fumbled with some wires in the back, "that we need to travel to get through the CTCs."

"The CT…er, what?" Kristoff asked, his left brow raised at what sounded vaguely like an insult at his mode of transport.

Anna watched as her sister closed a circuit in the back and turn a switch near a large metal enclosure that held three glass tubes of equal length. Another switch turned, then a viscous, blue substance slithered into the tubes.

With a slight smirk on her face, Elsa turned back towards the dashboard. "There." She placed the metal shades back at eye level.

"So what are you talking about, exactly?" Kristoff asked again.

"Sorry, what?" The metal shades glinted in the sun as Elsa turned to face the other two. "Oh. Right. You know, CTCs?" she cocked her head, then waited for a response. Hearing none (and seeing only befuddled expressions on the other two's faces), she continued, "Closed time-like curves?"

"No…?" he answered back. "Wait," he blinked rapidly, "what-I don't even-huh…"

"I _really_ don't have time to explain this right now," Elsa muttered.

Anna shook her head, then blinked at the three panels on the dashboard. Were those dates displayed on each panel, with the topmost one showing a year twenty years into the future, she wondered.

"Hoo-kay then…I'm gonna pretend, for all of us, that you're totally not being weird right now, Elsa…" Anna watched as her sister turned back towards the steering wheel, placing the grey shades back at eye level. "So I'm just gonna ask right now…what the heck is going on exactly?"

"Yeah," Kristoff added once he stopped sputtering in confusion, "I…I thought we were going on a road trip, you know, to surprise Anna?"

"Road…" Anna glanced at him, momentarily taken aback, "…trip?"

"This isn't," Elsa shook her head, then made a noise. "Ugh. We don't…" she grumbled something Anna couldn't quite make out, but somewhere in that barely audible litany she heard "capacitor" and something that sounded like a complaint about electrons or whatever it was that her sister geeked out about.

"Anyway. What's important is that we get to this point in time," she tapped on the top panel, "so we can _stop_ Hans!" Her grip on the steering wheel tightened.

"Hans?" Kristoff scratched his head. "Wait. _That_ Hans? Anna's ex?"

The doors swung back into position. The car whirred into life.

"Yes, _that_ Hans," Elsa sighed, exasperated that the other two couldn't seem to grasp what she was saying. It's as though she hadn't actually told them what had happened. "Weren't you listening to me? He's going to let the city freeze over twenty years from now. When he's elected as mayor."

The car began to accelerate away from the curb.

"Okay, first of all, you never said…" Anna paused, "Wait. What do you mean…" Anna growled. "He's going to be mayor?"

"Okay," Kristoff waved his hands, "hold on a sec. What do you mean he's going to be mayor when we're crusty old fortysomethings? And how do you even know this? That's twenty years into the future, Els."

"I'll explain. Later," her jaw tightened. "For now, just sit back, and enjoy the ride."


End file.
